Wire covering and tube forming die



Aug. 22, 1967 H. BURR 3,337,386

WIRE COVERING AND TUBE FORMING DIE Filed July 17, 1964 3 Sheets-Sheet 1 INVENTOR. 4 5 e BY HARVEY BURR HIS AGENT H. BURR Aug. 22, 1967 WIRE COVERING AND TUBE FORMING DIE Filed July 17, 1964 Z Sheets-Sheet 2 Fig. 4

Fig. 5

INVENTOR. HARVEY BURR MFMm/ Fig.6

HIS AGENT Aug. 22, 1967 H. BURR WIRE COVERING AND TUBE FORMING DIE 5 Sheets-Sheet 5 Filed July 17, 1964 Fig. 7

INVENTOR. HARVEY BURR HIS AGENT United States Patent Office 3,337,386 Patented Aug. 22, 1967 3,337,386 WIRE COVERING AND TUBE FORMING DIE Harvey Burr, De Kalb, Ill., assignor to Anaconda Wire and Cable Company, a corporation of Delaware Filed July 17, 1964, Ser. No. 383,335 6 Claims. (Cl. 156-585) ABSTRACT OF THE DISCLOSURE A heated die is used to apply a spiral wrap of paper insulation around a telephone wire such as is used in telephone cables of the type described in application Ser. No. 314,401, now Patent 3,300,714. The die cavity is formed so that the paper is not urged around the wire by pressure against its longitudinal edge but is urged by frictional engagement with a lengthwise groove in the die.

My invention relates to a die for continuously forming a strip of indefinite length into a tube having a substantial longitudinal overlap and particularly to a die for forming said tube around an advancing strand.

In the manufacture of insulated electric wires, such as telephone wires, it has been suggested in Patents 2,810,011 and 2,947,652 to wrap a single strip of paper insulation longitudinally around two wires to form a telephone pair that remains connected together by a paper web. For a number of reasons, however, it is desirable to apply the paper to a single wire instead of a pair. An important one of these reasons is the fact that it is easier to splice separately covered wires since they dont have to have the web slit with a razor blade as the webbed pairs do when they are spliced. Another reason for preferring separate wires is that they are more readily twisted together without disturbing the insulation.

No means have been available, however, for applying a longitudinal wrap around a single wire, as opposed to a pair of wires. When two wires are covered they complement each other in that the frictional resistance to folding the paper around one wire acts as the force urging the paper around the other wire. There is no such counterforce when only a single wire is being wrapped. Consequently, when efforts were made to bring pressure against the free edge of the paper to urge the other edge around the single Wire that was found to so stretch and warp the free edge that it would not lie flat. In this respect it should be noted that in the field of application of my invention the strips to be handled are very thin and delicate. For example No. 26 A.W.G. wire is wrapped with a strip only inch wide and 1.5 thousandths of an inch thick. In order to minimize cost and electrical capacitance between the two conductors there must be a minimum of paper and a maximum of air filling the space between them. Still there must be enough paper to provide a longitudinal overlap sufficient to avoid any bare spots when the pairs are twisted, and the cable is stranded, and this is not the case if the edge of the paper is warped and does not lie flat, but is, in elfect, wasted. If the edge of the paper is warped it has the further disadvantages of increasing the tendency of the paper insulation to unravel during splicing, and decreasing the longitudinal stiflness of the paper wrap. This stiflYness is important when tubular connectors are used of the type that is crimped down over insulated conductors.

A telephone conductor insulated by means of my apparatus has a tubular wrap of insulation with its edge extending substantially parallel to the conductor. This is opposed to known spirally-wrapped conductors in which the insulation is applied with a helical edge. My conductors have the advantage of longitudinal stifiness compared to helically wrapped conductors for the application of the above-mentioned tubular connectors, and, of course, there is much less tendency of my conductors to openat an overlapped edge and expose bare conductor when a cable is bent.

I have invented a die that is capable of applying a longitudinal wrap over a single wire in a very satisfactory manner. This has been accomplished by providing a curved side wall with its concave side facing the wire. This wall forms an acute angle with the line of advance of the wire and blends into the passage in the die through which the wire has been passing and forms part of that passage.

There is a longitudinal ledge against which the edge of the paper abuts, but only after it has made a half turn around the side wall curvature. Thus, the paper urged toward the wire, not only by the pressure against the edge of the strip, but by the frictional resistance against the curved side wall. Dies of this type are heated to set the paper in the desired shape as it passes through, and my die has the advantage that the edge of the paper which is initially farthest from the wire, rather than warping, it actually preset in a smooth arc that causes it to wrap permanently around the wire :at the exit end of the die. Although my die has particular utility for wrapping paper strip longitudinally around an advancing wire it can also be used to form a tube in the adbsence of any wire and will have utility for strips other than paper strips.

It have invented a die having an entrance end and an exit end for continuously forming an advancing strip, such as a paper strip, into a tube of indefinite length with a substantial overlap. My die may be used to wrap a strip of insulation around an advancing strand, and it comprises two parallel w alls defining a slot for the strip that diminishes in width from the entrance end toward the exit end of my die. It comprises a first and a second curvilinear side wall coextensive with the slot along its length with both side walls concave toward each other. My die also comprises a third curvilinear side wall concave toward the first side wall and forming a tubular passage in combination with the first side wall, which may be a strand-confining passage. My die also comprises a flat, strip-abutting side wall facing the second side wall. The third side Wall and the flat side wall converge and terminate short of the exit end of the die and the first side wall and second side wall converge and combine to form a tubular passage within the die. My die may comprise a first block having a first flat surface portion and a second block having a second flat surface portion with the slot being formed by a combination of these two portions. There are then means aligning these two blocks while permitting them to separate during the pass-age of thickened portions of strip through the die. There may also be a third block facing the first block with the first curvilinear side wall formed in the first block, the second curvilinear side wall formed in the third block, and the third curvilinear side wall formed in the second block, and means for heating the die.

A more thorough understanding of my invention may be gained from the appended drawing.

In the drawing:

FIGURE 1 is an end view of the apparatus of my invention.

FIGURE 2 is a side view of the apparatus of my invention.

FIGURE 3 is a top view of the hardened die inserts of my invention.

FIGURE 4 is an enlarged view of the entrance end of the die of FIGURE 3.

FIGURE 5 is an enlarged View of a section through the lines 55 of FIGURE 3.

FIGURE 6 is an enlarged view of a section through the lines 6-6 of FIGURE 3.

FIGURE 7 is an enlarged view of a section through the lines 7-7 of FIGURE 3.

Referring now to the drawing and particularly to FIG- URES 1 and 2, a strip-applying die indicated generally by the numeral 10 is comprised of a first block 11 which is uppermost and two lower blocks comprised of a second block 12 and a third block 13. This is the arrangement of the blocks that I have found to be most convenient but it will be understood that the blocks 12 and 13 might be placed uppermost and the block 11 underneath within the scope of my invention, or the die assembly might be rotated 45 or 90 degrees or some other angle. It will be further understood that the blocks 12 and 13 might be combined into a single block within the scope of my invention although the machining of such a single unit would be more difficult and expensive.

The blocks comprising the elements of my die 10 are aligned by means of a holder 14 which clamps the blocks 12, 13 between a shoulder 16 and a backing plate 17 urged by set screws 18, 19, 2t threaded into holes 21, 22, 23 in an upright extension 24 of the holder 14. The holder 14 has two end posts 26, 27 'pivotally mounting a gate 28 having a vertical back plate 29 and horizontal extension 31 integrally formed with the back plate. The gate 28 is rockingly suspended from the posts 26, 27 on two pins 32, 33 and can be locked by a pin 35. A long stud 34 is threaded through the center of the back plate 29 and in a loose fit through a bore 36 through the block 11. The stud 34 is also passed through a washer 37 which is retained against the block 11 by a compression spring 38. The end of the stud 34 is threaded through a length 39 to hold locking nuts 41, 42 to adjustably retain the spring 38. By these means it will be seen that the block 11 is urged to the left as viewed in the drawing. Movement to the left is restrained, however, by two pins 43, 44 which fit into recesses in set screws 46, 47 threaded into the back plate 29 and matching recesses 45 in the block 11 so that the position of the block 11 can be ad justed by turning the set screws.

The blocks 12, 13 are locked firrn'ly between the shoulder 16 and plate 17 but the block 11 is retained by spring compression and would be free to move forward slightly due to the frictional force of an advancing paper strip. To prevent this movement the horizontal extension 31 of the gate 28 is provided with a downwardly extending lug 48 having a tapped hole 49 for a set screw 50 with a hollow head 51 into which is fitted a pin 52. The pin 52 fits into an opening 53 and prevents forward movement of the block. The horizontal extension 31 has a tapped hole 54 for a threaded stud 56 which retains a compression spring 57 against the block 11. The stud 56 can be locked in any desired position by means of a locknut 58. The holder 14 has bores 59, 60 for respective heater elements 61, 62 and the block 11 has a bore 63 for a thermostat 64 of known type.

The working surfaces of my die 10 are subjected to constant abrasion by a heated strip of paper or other material and I prefer to provide the die blocks with hard carbide inserts for the working surfaces although it will be understood that my invention is by no means limited to the use of such inserts. Thus the block 11 has an insert 66 extending along its length and the blocks 12 and 13 have respective inserts 67, 68.

The novelty and utility of my invention can best be understood by reference to FIGURES 3, 4, 5, and 6. From FIGURE 4 which shows the entrance, or upstream end of my die in enlarged view, the insert 66 of the block 11 is seen to have a lower flat surface 69, which can be conveniently referred to as a first flat surface, and the insert 68 to have an upper flat surface 71, which can be conveniently referred to as a second flat surface, which, in combination, form a slot 72 for a strip of paper 73. Coextensive with the first surface 69 there is ground into the insert 66 a first curvilinear side wall 74 which is preferably semicircular. A second similar semicircular side wall 76 is ground in the upper right hand corner of the insert 67 in such a manner that it also can be made coextensive with the surface 69, and when the blocks 11, 12, 13 are assembled as shown, the side wall 76 forms an opposite extension of the slot 72 from the side wall 74. The fiat surface 69 is continuous to the left edge of the block 11 (as viewed in the drawings) and rests directly on an upper surface 77 of the block 12. In order, however, to provide space for the slot 72 the surface 71 is lower than the surface 77 and does not, of course, help support the block 11. The right side of this block as seen in the figures) has a flat surface 78 which is supported on an upper surface 79 of the block 13. The vertical distance between the surfaces 69 and 79 equal the diameter of the semicircles formed by the curvilinear walls 74 and 76.

The surface 79 curves upwardly to form a third curvilinear wall 81 in the insert 68 and the walls 74, 81 combine to form a lengthwise passage in my die 10 for a wire or other strand 82. Bell mouths 83, 84, 85 are provided at the entrance ends of the respective inserts 66, 67, 68 to facilitate threading the paper into the die and to ease the admission of lumps and lapped splices in the strip as it is continuously pulled through the die along with the strand 82 by capstan or other known take-up means, not shown.

It can be seen in FIGURE 4 that when the paper strip 73 first enters the die, the greatest portion of its width is flat due to the fact that the slot 72 has a width at the entrance at least equal in extent to a major portion of the width of the strip. The strip is curved slightly in a curl 86 around the outside of the strand 82 against the wall 74 and it is curved an approximately equal amount in a curl 87 against the curvilinear wall 76. However, a die may be constructed within the scope of my invention in which the slot 72 is wide enough to accommodate a strip without curling the edges. FIGURE 5 shows a section through the die at a point downstream of the entrance. Here the surface 71 has narrowed considerably from its width at the entrance with the result that the slot 72 is narrower at this section. The curls 86, 87 have been forced by the narrowing of the slot into full semicircles around the curvilinear walls '74, 76. At this point, however, a left edge 88 of the strip 73 has abutted against a flat surface 89 of the block 13 which, in its upper portion, constitutes a flat side wall facing the curvilinear wall 76. As the paper continues to advance, since it cannot curl any further along the wall 76, the curl 86 grows larger at an increased rate and an edge 91 of the strip curves along the curvilinear wall 81 to complete the circle around the strand 82 (FIGURE 6). As the strip continues to advance, the edge 91 pushes around the wire 82.

The thermostat 64 maintains the die at a temperature generated by the heaters 61 and 62 sufficient to drive steam from the paper in its passage through the die which has the effect of lubricating it. It is important to note, however, that the resistance against the insertion of the edge 91 is not transmitted directly to the edge 88, abutting the flat wall 89, but pushes the entire curl 87 against the curvilinear wall 76. This has a capstan effect so that very little force is actually transmitted to the edge 88 and the latter is not warped or distorted, because the end pressure is not suflicient to create such warping. Although it does take considerable pressure to force the edge 91 around the strand, this pressure is mostly supplied by the friction of the curl 87 against the wall 76.

By the time the strip has reached the section shown in FIGURE 7 the edge 91 has been forced half-way again around the strand 82 so that it is now at a point beneath the stnand. However, the walls 89 and 81 of the insert 68 have been converging and have now disappeared so that the strand passage is now comprised of the walls 74 and 76 instead of the walls 74 and 81. The curl 87 'now surrounds the strand so that there are two complete turns of strip around the strand, although it will be understood that a lesser or greater overlapping of the strip may be made within the scope of my invention. The covered strand completes its passage through the die in this form in which it is permanently set by the ironing effect of the high temperature.

In the operation of my invention my die is originally opened by removing the locking pin 35 and swinging up the gate 28 on the pins 32, 33. By this means the block 11 is separated from the blocks 12, 13. The strand 82 is connected to a known type of take-up, not shown, and laid on the block insert 68 against the curved wall 81. The strip 73 is positioned by hand on the fiat surface 71 and the leading end of the strip is rolled around the strand by hand so that it conforms to the lower portion of the die. The block 11 is then lowered into place by swinging down the gate 28 and the pin 35 is reinserted. The die is brought up to temperature by means of the heater elements 61, 62 and the take-up is started, drawing both the strand 82 and the strip 73 through the die, from which the strand emerges with the strip longitudinally wrapped around it.

When an imperfection or a splice in the strip 73 enters the die 10 the block 11 lifts slightly against the spring 57. This is possible because the stud 34 has some freedom of movement in the oversized bore 36. However, when the imperfection or lump has passed through and the block 11 returns to rest on the blocks 12, 13 it is in perfect alignment due to the construction of my die, described hereinabove, including the pins 43, 44 and 52.

The die of my invention has proven eminently successful for covering telephone conductor wire with paper insulation and I have found that the following dimensions and thicknesses of strip are to be preferred for this purpose:

Wire size, A.W.G. Paper width, Paper thickness,

inches inches 26 Va 0015 24 M 002 22 7in 0025 19 /i6 0035 tinuously forming an advancing strip into a tube of in-' definite length having a substantial longitudinal overlap, comprising:

(A) two parallel walls defining a slot for said strip,

(a) said slot diminishing in width from the entrance end toward the exit end of said die, (B) a first curvilinear side wall coextensive with said slot along the length thereof, (C) a second curvilinear side wall coextensive with said slot along the length thereof,

(a) said side walls being concave toward each other, (D) a third curvilinear side wall (a) concave toward said first side wall (b) forming a tubular passage in combination therewith, and (E) a flat, strip-abutting, side wall (a) facing said second side wall, (F) said third side wall and said flat side wall converging, and terminating short of the exit end of said die,

(G) said first side wall and said second side wall converging, and combining to form. a tubular passage within said die.

2. A die having an'entrance end and an exit end for continuously forming a advancing strip into a tube of indefinite length having a substantial longitudinal overlap, comprising:

(A) a first block having a first flat surface portion,

(B) a second block having a second flat surface portion,

(a) said first and said second portions combining to form a slot diminishing in width from the entrance end toward the exit end of said die,

(C) means aligning said first block and said second block (a) while permitting said blocks to separate during the passage of thickened portions of strip through the die,

(D) a first curvilinear side wall coextensive with said slot along the length thereof,

(E) a second curvilinear side wall coextensive with said slot along the length thereof,

(a) said side walls being concave toward each other,

(F) a third curvilinear side wall (a) concave towardsaid first side wall (b) forming a tubular passage in combination therewith, and

(G) a flat, strip-abutting side wall (a) facing said second side wall,

(H) said third side wall and said flat. side wall convergiing, and terminating short of the exit end of said (I) said first side wall and said second side wall converging, and combining to form a tubular passage within said die.

3. A die having an entrance end and an exit end for continuously forming an advancing strip into .a tube of indefinite length having a substantial longitudinal overlap, comprising:

(A) a first block having a first flat surface portion,

(B) a second block having .a second flat surface portion,

(a) said first and second portions combining to form a slot diminishing in width from the entrance end toward the exit end of said die,

(C) means aligning said first block and said second blocks (a) while permitting said blocks to separate during the passage of thickened. portions of strip through the die,

(D) a first curvilinear side wall (a) formed in said first block,

(b) coextensive with said slot,

(0) along the length thereof,

(E) a third block facing said first block,

(F) a second curvilinear side wall (a) formed in said third block,

(b) coextensive with said slot along the length thereof,

(c) said side walls being concave toward each other,

(G) a third curvilinear side wall (a) formed in said second block,

(b) concave toward said first side wall,

(c) forming a tubular passage in combination therewith, and

(H) a flat, strip-abutting, side wall (a) formed in said second block,

(b) facing said second side wall,

(I) said third side wall and said flat side wall converging, and terminating short of the exit end of said 'die,

(J) said first side wall and said second side wall converging, and combining to form a tubular passage within said die.

4. A die having an entrance end and an exit end for continuously wrapping a paper strip with a substantial longitudinal overlap around an advancing strand, comprising:

(A) two parallel walls defining a slot for said strip,

(a) said slot diminishing in width from the entrance end toward the exit end of said die,

(B) a first curvilinear side wall coextensive with said slot along the length thereof,

(C) a second curvilinear side wall coextensive with said slot along the length thereof,

(a) said side walls being concave toward each other,

(D) a third curvilinear side wall (a) concave toward said first side wall (b) forming a tubular, strand-confining, passage in combination therewith, and

(E) a Hat, strip-abutting, side wall (a) facing said second side wall,

(F) said third side wall and said fiat side wall converging, and terminating short of the exit end of said die,

(G) said first side wall and said second side wall converging, a'nd combining to form a tubular passage within said die, and

(H) means for heating said die.

5. A die having an entrance end and .an exit end for continuously wrapping a paper strip with a substantial longitudinal overlap around an advancing strand, comprising:

(A) a first block having a first fiat surface portion,

(B) a second block having a second fiat surface portion,

(a) said first and second portions combining to form a slot diminishing in width from the entrance end toward the exit end of said die,

(C) means aligning said first block and said second block (a) while permitting said blocks to separate during the passage of thickened portions ofv strip through the die,

(D) a first curvilinear side wall coextensive with said slot along the length thereof,

(E) a second curvilinear side wall coextensive with said slot along the length thereof,

(a) said side walls being concave toward each other,

(F) a third curvilinear side wall (a) concave toward said first side wall,

(b) forming a tubular, strand-confining, passage in combination therewith, and

(G) a fiat, strip-abutting, side wall (a) facing said second side wall,

(H) said third side wall and said flat side wall converging, and terminating short of the exit end of said die,

(I) said first side wall and said second side wall converging, and combining to form a tubular passage short of the exit end. of said die, and

(J) means for heating said die.

6. A die having an entrance end :and an exit end for continuously wrapping a paper strip with a substantial longitudinal overlap around an advancing strand, comprising:

(A) a first block having a first flat surface portion,

(B) a second block having a second fiat surface portion,

(a) said first and said second portions combining to form a slot diminishing in width from the entrance end toward the exit end of said die,

(C) means aligning said first block and said second block (a) while permitting said blocks to separate during the pass-age of thickened portions of strip through the die,

(D) a first curvilinear side wall (a) formed in said first block, (b) coextensive with said slot, (c) along the length thereof, (E) a third block facing on said first block, (F) a second curvilinear side wall (a) formed in said third block, (b) coextensive with said slot along the length thereof, (0) said side walls being concave toward each other,

(G) a third curvilinear side wall,

(a) formed in said second block,

(b) concave toward said first side wall,

(c) forming a tubular, strand-confining, passage in combination therewith, and

(H) a flat, strip-abutting, side wall (a) formed in said second block, (b) facing said second side wall,

(I) said third side wall and said fiat side wall converging, and terminating short of the exit end of said die,

(I) said first side wall and said second side wall converging, and combining to form a tubular passage short of the exit end of said die, and

(K) means for heating said die.

References Cited UNITED STATES PATENTS Isenberg 15 6-466 XR EARL M. BERGERT, Primary Examiner.

PHILIP DIER, Examiner. 

1. A DIE HAVING AN ENTRANCE AND AN EXIT END FOR CONTINUOUSLY FORMING AN ADVANCING STRIP INTO A TUBE OF INDEFINITE LENGTH HAVING A SUBSTANTIAL LONGITUDINAL OVERLAP COMPRISING: (A) TWO PARALEL WALLS DEFINING A SLOT FOR SAID STRIP (A) SAID SLOT DIMINISHING INWIDTH FROM THE ENTRANCE END TOWARD THE EXIT END OF SAID DIE, (B) A FIRST CURVILINEAR SIDE WALL COEXTENSIVE WITH SAID SLOT ALONG THE LENGTH THEREOF, (C) A SECOND CURVILINEAR SIDE WALL COEXTENSIVE WITH SAID SLOT ALONG THE LENGTH THEREOF, (A) SAID SIDE WALLS BEING CONCAVE TOWARD EACH OTHER, (D) A THIRD CURVILINEAR SIDE WALL (A) CONCAVE TOWARD SAID FIRST WALL (B) FORMING A TUBULAR PASSAE IN COMBINATION THEREWITH, AND (E) A FLAT, STRIP-ABUTTING, SIDE WALL (A) FACING SAID SECOND SIDE WALL, (F) SAID THIRD SIDE WALL AND SAID WALL CONVERGING, AND TERMINATING SHORT OF THE EXIT END OF SAID DIE, (G) SAID FIRST SIDE ALL AND SAID SECOND SAID WALL CONVERGING, AND COMBINING TO FORM A TUBULAR PASSAGE WITHIN SAID DIE. 